This application for shared instrumentation requests partial support for the purchase of a replacement position tomograph for preclinical research to be located in The University of Michigan Cyclotron/PET Center. A number of NIH-funded investigators have research needs for determining the biodistribution of a positron-labeled radiotracers in experimental animals. At present, the Cyclotron/PET facility makes use of a dedicated, 18-year old animal PET that has now become unserviceable. This grant requests funds to replace the existing tomograph with a modern, functional scanner capable of imaging primate brain as well as well as other small animals with high anatomic resolution and good sensitivity. The proposed replacement tomograph will permit not only the continuation of ongoing NIH-supported research, but will facilitate the development of new projects and users in emerging areas of radiotracer biomedical imaging. A major prior use of preclinical PET imaging was in the development and characterization of novel radiotracers. After initial biodistribution studies in small animal models (usually rodents), in vivo primate imaging studies are performed to verify the suitability of the radiotracer and the chosen analytical approach before extending the new tracer to human clinical studies. This will continue to be an essential research function served by the replacement tomograph. A second major area of tomograph utilization involves targeted research in animal models of neurological, cardiac and oncological disorders. The ability to determine radiotracer distributions non-invasively with PET permits the design of longitudinal experimental protocols. This considerably reduces the numbers of animals needed in comparison to designs employing invasive invasive measures of tracer distribution, and is particularly essential to experiments where significant inter-individual variability is expected (e.g.: some experimental lesion models, gene transfection studies, etc.) Or where there is considerable investment in the animals (e.g. primate studies).